Develop Reference

Android Studio: Repoen App with Previous Screen

I'm writing an app with 8 different Activities that are all interconnected(accessible from one another). I'm wondering how I can have the app always reopen from a full close (not just home button click but from closing the background activity) with the same screen it was exited from.
For example, from my Splash Screen I navigate to a home screen. From that home screen I navigate to the Settings. Now, I click the multi-tab viewer and close all apps. How can I have Settings(or wherever I had left off) become the launching activity when the app is reopened?
Thanks in advance!

You can use SharedPreferences to store the class name of the latest Activity. Later, when relaunch, you can redirect to it from the Splash Screen.

You can do that simply by using SharedPreferences. When you launch an activity, it changes it's last activity value in SharedPreferences to point at that activity.
When you close the app and then reopen it, your Main/Launcher activity (Which may be your Splash Screen) then checks for this value and launches the activity according to this value which represents the last activity the app was on.
Here is the code that would fit the Main/Launcher activity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String lastActivity = getDefaults("LAST_ACTIVITY", MainActivity.this);
Intent intentLastActivity;
// use an if statement to find out which activity it is
if(!lastActivity.equals("") || !lastActivity.equals(null)){
if(lastActivity.equals("home")){
intentLastActivity = new Intent(MainActivity.this, HomeActivity.class);
}else if(lastActivity.equals("settings")){
intentLastActivity = new Intent(MainActivity.this, SettingsActivity.class);
// add more else-if statements for the other activities.
}
startActivity(intentLastActivity); // launch the last activity
finish(); // finish/close the current activity.
}
}
public static void setDefaults(String key, String value, Context context) {
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
SharedPreferences.Editor editor = preferences.edit();
editor.putString(key, value);
editor.apply();
}
public static String getDefaults(String key, Context context) {
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
return preferences.getString(key, null);
}
Once that code is placed in your Main/Launcher activity. You can then set this last activity value in SharedPreferences in other activities when they are launched.
Code placed in the other activities (in the onCreate method):
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
// we are at the settings activity. Change last activity value to settings
MainActivity.setDefaults("LAST_ACTIVITY","settings",this);
}
Luckily the methods to change the last activity are accessible in other activities.
If you're able to implement this well in your app. It should work as you want it to.
HOPE THIS HELPS!

Resuming last activity on icon press to set result

I am trying to re-open last activity on icon press. But it starts from splash when I remove launchMode SingleTask from main.
Below is the scenario -
A = Splash , B = Activity1 , C = Activity 2.
I want to launch C on icon press.
On Start
A ---->B---->C (Here home icon pressed)
On Click Icon It runs A but I want C . Can any one solve this?
Launching C-
Intent urlIntent = new Intent(this,C.class);
urlIntent.putExtra("stt",Str);
startActivityForResult(urlIntent,REQUEST_CODE);

CASE I. Check if your app is in background after pressing the home button. If it is then it should open activity C.
CASE II. If your app is killed due to low on memory then it will start from launcher activity i.e. activity A.
I also faced this issue. This issue occurred due to changed setting of device.If user enable "Don't keep activities" then all activities will be destroyed if you press home or start new activity.
Note: I used the default launch mode

Your app will always start from the Activity with the filter intent.action.MAIN in the Manifest.xml.
And if your application is already running then the next time time your app starts it will automatically resume from the last opened activity.
Now if your app gets killed or swiped out then you can store the activity in SharedPreferences when activity is resumed or paused and on next start check in your spash which is Activity 'A' in your case, which was the last opened activity as you had stored the Activity name in SharedPreferences.
Example :
If you have three activities A-->B-->C
store the name in onPause() of all activities use SharedPreference to store its name :
#Override
protected void onPause() {
super.onPause();
SharedPreferences prefs = getSharedPreferences("Pref", MODE_PRIVATE);
SharedPreferences.Editor editor = prefs.edit();
editor.putString("lastOpenedActivity", getClass().getName());
editor.apply();
}
And in your Splash which is here Activity A use this preference to checfk in your onCreate() -
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Class lastActivity;
try {
SharedPreferences prefs = getSharedPreferences("Pref", MODE_PRIVATE);
lastActivity = Class.forName(prefs.getString("lastOpenedActivity", ParentActivity.class.getName()));
} catch (ClassNotFoundException ex) {
lastActivity = ParentActivity.class;
}
startActivity(new Intent(this, lastActivity));
this.finish();
}

how to start from different Activity in android studio

i make app with two activities.
firs has:
2 ExitText(login and password);
button(confirm, save data with SharedPreferences, intent to second activity).
second one:
2 TextView(get login and password with SharedPreferences);
button(clear data on SharedPreferences, intent to firsActivity).
how to make next: while there are some data on SharedPreferences - app will be started from the 2nd screen.
for example, i made:
if (user!=null && pass!=null){ Intent enterIntent = new Intent(MainActivity.this,SecondActivity.class);
startActivity(enterIntent);
}
but, technically it first run the firstActivity and than go to the secondOne. if there are some method to start app with the another activity (not mainOne)?

You won't be able to check to see if there are values in SharedPreferences before entering one Activity.
What you can do is check the value before displaying the UI (before calling setContentView(R.layout.my_layout)), and either continue along, or start the next Activity.
public class MyStartActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SharedPreferences preferences = getSharedPreferences("my_prefs", Context.MODE_PRIVATE);
if (preferences.contains("my_key")) {
// start next Activity
}
setContentView(R.layout.my_layout);
}
}

If you don't want the first one on the back stack, you can call finish() after starting the second one (or use appropriate flag(s) on intent).
Another approach would be to have only one activity with to fragments and decide dynamically which one set on start. With fragments you can also easily change layouts on button click or on back pressed.

I'm not sure if it will work, because app has to start at the first activity. First activity checks login and pass at share preferences and then you can go to the second activity

try this
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SharedPreferences preference = getSharedPreferences("my_prefs", Context.MODE_PRIVATE);
if (preference.getSting("key",null)!= null) {
// start new Activity
//finish this activity so it not in back stack
} else {
setContentView(R.layout.my_layout);
}
}

return to the same activity, When restart the app

I have a lot of activities in my app, and I want that if the user closes the app in activity 13 for example, when opening the app at another time the activity returns in activitty n° 13. how can I do this? thank in advance

You could use SharedPreferences to keep track of the last used activity.
Then you can redirect the user in the onCreate of your main activity to the correct activity, and call finish on your main activity.
This could look something like this:
#Override
protected void onCreate(Bundle savedInstanceState)
(...)
int last_activity = getLastActivityIdFromSharedPreferences();
if (last_activity == 1)
{
this.startActivity(new Intent(this, ActivityOne.class));
finish();
}
(...)
}

Android MainActivity calls another Activities, after pressing back key, blank screen shows

my main.xml file is just dummy. I want to start different activites based on the condition. If the password is found in shared pref file, the login activity should be launched, and if password is not found, the configuration activity should be launched. it is working fine but when I press the back key from keypad, the main activity is shown (I mean the blank screen because there is nothing) How can I avoid this?
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
prefs = getSharedPreferences(preffilename, MODE_PRIVATE);
final String password = prefs.getString("password",null);
if(password == null)
{
Intent i = new Intent(getApplicationContext(), Configuration.class);
startActivity(i);
}
else
{
Intent i = new Intent(getApplicationContext(), Login.class);
startActivity(i);
}
}

Call finish() from your main activity after calling startActivity(), this will remove main activity from stack.

What is your expectation when you pressed the back button? You might want to put those code in onResume() so it always get called when the main activity is brought back from the stack.